An air turbine starter (ATS) is typically used to start an aircraft turbine engine, for example, a gas turbine jet engine. The ATS is typically mounted to the jet engine through a gearbox or other transmission assembly and a cover plate or wall is located between the starter and gearbox housings. The gearbox transfers power from the ATS to the engine to start the engine.
Many air turbine starters typically include lubrication to run properly. Some air turbine starters use an assisted wet cavity design (AWC) to assist in lubrication. These designs include a turbine starter housing having a mounting face or mounting flange that is sealingly engaged with, and coupled to, the gearbox such that a porting system, that allows free transfer of lubricating oil between the gearbox and the starter, is defined. Each port in the porting system is typically in fluid communication with passages within the starter housing so that oil can be distributed within the starter, and are located in portions of the starter-gearbox assembly such that they act as sump passages or oil return passages.
Typically in AWC designs, air flows freely between the starter and the gearbox. The gearbox may be pressurized or nonpressurized. In a non-pressurized gearbox design, the gearbox pressure may be about 0.1–0.3 psi above ambient pressure. At times, the starter housing may become punctured, causing a breach in the starter structure and a change in pressure. In such case, the starter pressure may drop to equalize with ambient pressure. Consequently, in the case of the non-pressurized design, the pressure differential between the gearbox and starter may be about 0.1 to 0.3 psi. Though this pressure differential may be relatively small, excessive oil may still leak from the gearbox to the starter and, consequently, out through the breach. Generally, in such an event, a check or reed valve is used to counteract the oil loss. However, because the pressure differential between the starter and gearbox is small, it has been found that these valve types may not work consistently.
Accordingly, there is a need for an aircraft turbine starter with improved fluid flow control in the condition of starter housing puncture. Additionally, there is a need for an air turbine starter with the ability to operate during starter housing breach, and in particular, in instances when the breach causes a low pressure differential between the starter and gearbox. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.